SAM CLI: Serverless Made Simple (or million lines terraform?)

Still deploying Lambda functions by hand?

We’ve all been there: manually zipping code, uploading to S3, configuring triggers, setting up API Gateway… it’s enough to make you question if serverless is actually worth it. Or worse, writing hundreds of lines of Terraform just to deploy a simple function.

Enter AWS SAM CLI

AWS Serverless Application Model (SAM) CLI is the tool that will make you fall in love with serverless development again. It’s like Docker Compose for Lambda functions.

# Install it
brew install aws-sam-cli

The 30-second serverless app

Create a new project:

sam init

Choose the “Hello World Example” with Python, and you’ll get a project structure like this:

my-app/
├── hello_world/
│   ├── __init__.py
│   ├── app.py
│   └── requirements.txt
├── events/
│   └── event.json
├── template.yaml
└── tests/

The magic is in template.yaml, which defines your entire application:

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: hello_world/
      Handler: app.lambda_handler
      Runtime: python3.9
      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /hello
            Method: get

Test locally (yes, really!)

sam local invoke

Or start a local API (Requires docker):

sam local start-api

Deploy with a single command

sam deploy --guided

This builds your code, packages it, creates/updates the CloudFormation stack, and gives you an API endpoint. All from one command!

Pro tip: Use SAM Accelerate for faster iterations

sam sync --watch

This watches for file changes and automatically syncs them to the cloud. No full redeployment needed.

No more excuses for not going serverless. SAM CLI makes it almost too easy!